The former head of the National Security Agency (NSA) has compared Edward Snowden, who leaked a host of the agency's top secret documents, to both "the Boston bombers" and Benedict Arnold.

In a rare interview with the Australian Financial Review Friday, former general Michael Hayden sharply criticized Snowden, the former NSA contractor who in June fled the country with a host of documents that detail how the agency spies on Americans' phone calls and the world's Internet use.

Hayden particularly cautioned against a culture that promotes transparency as a virtue, as he feels that's an attitude that can damage national security:

The issue is at what point does Islamic fundamentalism flip-over and become a genuine national security threat? Likewise, at what point does a cultural tendency towards transparency flip-over to become a deep threat inside your system? They are similar issues.

"I personally think Snowden is a very troubled, narcissistic young man who has done a very, very bad thing," he added.

It's part of what appears to be something of a media campaign in which Hayden defends NSA practices and speaks ill of Snowden.

In a CNN editorial also published Friday, Hayden said Snowden "will likely prove to be the most costly leaker of American secrets in the history of the republic."

Snowden's biggest leaks include evidence that the NSA taps American companies for their users's communications through programs like PRISM.

They also revealed that the NSA gets court orders for the metadata of likely every Americans's phone calls. Ironically, other documents provided by Snowden show that Hayden, in fact, helped shepherd that program into existence in the immediate aftermath of 9/11. A leaked, secret court order for Verizon to provide all their metadata to the NSA was set to expire and probably be renewed Friday. It's unclear if Hayden's timing was meant to coincide.

Hayden did, at least, grant Snowden the benefit of the doubt that he was motivated by ideals, and not by money or a lack of patriotism.

"He seems to have revealed this information because of his ideological embrace of transparency as a virtue," he told the Australian Financial review.

On CNN, Hayden offered the same sentiment. "After all, he believes he is acting for a higher good—an almost romantic attachment to the merits of absolute transparency."